Gravitation 11th Science Lessons
Gravitation 11th Science Lessons
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Question 1 of 82
1. Question
Which of these 17th century theory explained the motion of celestial and terrestrial objects?
Correct
The ‘Theory of Gravitation’ was developed by Newton in the late 17thcentury to explain the motion of celestial objects and terrestrial objects and answer most of the queries raised. In spite of the study of gravitation and its effect on celestial objects, spanning last three centuries, “gravitation” is still one of the active areas of research in physics today.
Incorrect
The ‘Theory of Gravitation’ was developed by Newton in the late 17thcentury to explain the motion of celestial objects and terrestrial objects and answer most of the queries raised. In spite of the study of gravitation and its effect on celestial objects, spanning last three centuries, “gravitation” is still one of the active areas of research in physics today.
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Question 2 of 82
2. Question
For which of this discovery Albert Einstein was awarded Nobel Prize in 2017?
Correct
In 2017, the Nobel Prize in Physics was given for the detection of ‘Gravitational waves’ which was theoretically predicted by Albert Einstein in the year 1915.
Incorrect
In 2017, the Nobel Prize in Physics was given for the detection of ‘Gravitational waves’ which was theoretically predicted by Albert Einstein in the year 1915.
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Question 3 of 82
3. Question
Who was the first person to explain the geocentric model?
Correct
In the second century, Claudius Ptolemy, a famous Greco-Roman astronomer, developed a theory to explain the motion of celestial objects like the Sun, the Moon, Mars, and Jupiter etc. This theory was called the geocentric model.
Incorrect
In the second century, Claudius Ptolemy, a famous Greco-Roman astronomer, developed a theory to explain the motion of celestial objects like the Sun, the Moon, Mars, and Jupiter etc. This theory was called the geocentric model.
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Question 4 of 82
4. Question
Choose the correct statements.
i) The Earth is at the centre of the universe and all celestial objects orbit the earth except the Sun in the geocentric model.
ii) Ptolemy’s model does not match with the naked eye observations of Sky.
iii) Ptolemy’s model did not explain the motion of Mars and Jupiter effectively.Correct
According to the geocentric model, the Earth is at the centre of the universe and all celestial objects including the Sun, the Moon, and other planets orbit the Earth. Ptolemy’s model closely matched with the observations of the sky with our naked eye. But later, astronomers found that even though Ptolemy’s model successfully explained the motion of the Sun and the Moon up to a certain level, the motion of Mars and Jupiter could not be explained effectively.
Incorrect
According to the geocentric model, the Earth is at the centre of the universe and all celestial objects including the Sun, the Moon, and other planets orbit the Earth. Ptolemy’s model closely matched with the observations of the sky with our naked eye. But later, astronomers found that even though Ptolemy’s model successfully explained the motion of the Sun and the Moon up to a certain level, the motion of Mars and Jupiter could not be explained effectively.
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Question 5 of 82
5. Question
In which century Nicholas Copernicus proposed the heliocentric model?
Correct
In the 15th century, a Polish astronomer, Nicholas Copernicus (1473-1543) proposed a new model called the ‘Heliocentric model’.
Incorrect
In the 15th century, a Polish astronomer, Nicholas Copernicus (1473-1543) proposed a new model called the ‘Heliocentric model’.
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Question 6 of 82
6. Question
Which of the following is not correct regarding the heliocentric model?
Correct
A Polish astronomer, Nicholas Copernicus (1473-1543) proposed a new model heliocentric model. In the ‘Heliocentric model’ the Sun was considered to be at the centre of the solar system and all planets including the Earth orbited the Sun in circular orbits. This model successfully explained the motion of all celestial objects.
Incorrect
A Polish astronomer, Nicholas Copernicus (1473-1543) proposed a new model heliocentric model. In the ‘Heliocentric model’ the Sun was considered to be at the centre of the solar system and all planets including the Earth orbited the Sun in circular orbits. This model successfully explained the motion of all celestial objects.
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Question 7 of 82
7. Question
Who discovered that all objects are accelerated towards the Earth?
Correct
Around the same time, Galileo, a famous Italian physicist discovered that all objects close to Earth were accelerated towards the Earth at the same rate.
Incorrect
Around the same time, Galileo, a famous Italian physicist discovered that all objects close to Earth were accelerated towards the Earth at the same rate.
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Question 8 of 82
8. Question
Whose observations were used to form the Kepler’s law of planetary motion?
Correct
A noble man called Tycho Brahe (1546-1601) spent his entire lifetime in recording the observations of the stellar and planetary positions with his naked eye. The data that he compiled were analysed later by his assistant Johannes Kepler (1571–1630) and eventually the analysis led to the deduction of the laws of the planetary motion. These laws are termed as ‘Kepler’s laws of planetary motion’.
Incorrect
A noble man called Tycho Brahe (1546-1601) spent his entire lifetime in recording the observations of the stellar and planetary positions with his naked eye. The data that he compiled were analysed later by his assistant Johannes Kepler (1571–1630) and eventually the analysis led to the deduction of the laws of the planetary motion. These laws are termed as ‘Kepler’s laws of planetary motion’.
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Question 9 of 82
9. Question
Which of these statements are not true regarding the Kepler’s law of Orbits?
i) All the planets move around the Sun in an elliptical orbit.
ii) The Closest point of approach of the planet to the Sun foci is called as perihelion.
iii) Copernicus and Ptolemy considered the planets orbits to be elliptical around the Sun.Correct
Explanation
Kepler’s laws are stated as follows: Law of orbits: Each planet moves around the Sun in an elliptical orbit with the Sun at one of the foci. The closest point of approach of the planet to the Sun ‘P’ is called perihelion and the farthest point ‘A’ is called aphelion. The semi-major axis is ‘a’ and semi-minor axis is ‘b’. In fact, both Copernicus and Ptolemy considered planetary orbits to be circular, but Kepler discovered that the actual orbits of the planets are elliptical.Incorrect
Explanation
Kepler’s laws are stated as follows: Law of orbits: Each planet moves around the Sun in an elliptical orbit with the Sun at one of the foci. The closest point of approach of the planet to the Sun ‘P’ is called perihelion and the farthest point ‘A’ is called aphelion. The semi-major axis is ‘a’ and semi-minor axis is ‘b’. In fact, both Copernicus and Ptolemy considered planetary orbits to be circular, but Kepler discovered that the actual orbits of the planets are elliptical. -
Question 10 of 82
10. Question
Assertion (A): The Planets travel at varying speeds around the Sun to cover equal area in equal intervals of time.
Reasoning(R): The Sun is not at the centre of ellipse so the planets travel faster near the sun and slower when they are fartherCorrect
The radial vector (line joining the Sun to a planet) sweeps equal areas in equal intervals of time. The white shaded portion is the area DA swept in a small interval of time Dt, by a planet around the Sun. Since the Sun is not at the centre of the ellipse, the planets travel faster when they are nearer to the Sun and slower when they are farther from it, to cover equal area in equal intervals of time. Kepler discovered the law of area by carefully noting the variation in the speed of planets.
Incorrect
The radial vector (line joining the Sun to a planet) sweeps equal areas in equal intervals of time. The white shaded portion is the area DA swept in a small interval of time Dt, by a planet around the Sun. Since the Sun is not at the centre of the ellipse, the planets travel faster when they are nearer to the Sun and slower when they are farther from it, to cover equal area in equal intervals of time. Kepler discovered the law of area by carefully noting the variation in the speed of planets.
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Question 11 of 82
11. Question
Which of the following statement is not correct regarding the time period of revolution of a planet around the sun?
Correct
The square of the time period of revolution of a planet around the Sun in its elliptical orbit is directly proportional to the cube of the semi-major axis of the ellipse. It can be written as: where, T is the time period of revolution for a planet and a is the semi-major axis. Physically this law implies that as the distance of the planet from the Sun increases, the time period also increases but not at the same rate.
Incorrect
The square of the time period of revolution of a planet around the Sun in its elliptical orbit is directly proportional to the cube of the semi-major axis of the ellipse. It can be written as: where, T is the time period of revolution for a planet and a is the semi-major axis. Physically this law implies that as the distance of the planet from the Sun increases, the time period also increases but not at the same rate.
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Question 12 of 82
12. Question
State the constant value relating Kepler’s third law.
- a) T5 / a4
- b) T2 / a3
- c) T3 / a5
- d) T2 / a
Correct
The time period of revolution of planets around the Sun along with their semi-major axes are given. We can realize that T2 / a3 are nearly a constant endorsing Kepler’s third law.
Incorrect
The time period of revolution of planets around the Sun along with their semi-major axes are given. We can realize that T2 / a3 are nearly a constant endorsing Kepler’s third law.
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Question 13 of 82
13. Question
Which of the planet takes around 165 years around the Sun?
Correct
Incorrect
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Question 14 of 82
14. Question
Identify the Incorrect Match of the Planet and the revolution time around the sun.
- Venus i) 0.615yrs
- Jupiter ii) 29.55yrs
- Uranus iii) 84yrs
- Mars iv) 1.88yrs
Correct
Incorrect
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Question 15 of 82
15. Question
Which of these laws endorse the value of the T2 / a3 as constant?
Correct
The time period of revolution of planets around the Sun along with their semi-major axes are given. we can realize that T2 / a3 is nearly a constant endorsing Kepler’s third law.
Incorrect
The time period of revolution of planets around the Sun along with their semi-major axes are given. we can realize that T2 / a3 is nearly a constant endorsing Kepler’s third law.
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Question 16 of 82
16. Question
Which of the following person analysed the Kepler’s law?
Correct
Even though Kepler’s laws were able to explain the planetary motion, they failed to explain the forces responsible for it. It was Isaac Newton who analysed Kepler’s laws, Galileo’s observations and deduced the law of gravitation
Incorrect
Even though Kepler’s laws were able to explain the planetary motion, they failed to explain the forces responsible for it. It was Isaac Newton who analysed Kepler’s laws, Galileo’s observations and deduced the law of gravitation
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Question 17 of 82
17. Question
Choose the Incorrect statements.
- i) Newton’s law of gravitation states that any particle is attracted by other particle with an attractive force.
- ii) The strength of the attraction force is directly proportional to the product of the masses.
- iii) The Square of the distance between the particles is also directly varies proportional to the force of attraction.
Correct
Newton’s law of gravitation states that a particle of mass M1 attracts any other particle of mass M2 in the universe with an attractive force. The strength of this force of attraction was found to be directly proportional to the product of their masses and is inversely proportional to the square of the distance between them.
Incorrect
Newton’s law of gravitation states that a particle of mass M1 attracts any other particle of mass M2 in the universe with an attractive force. The strength of this force of attraction was found to be directly proportional to the product of their masses and is inversely proportional to the square of the distance between them.
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Question 18 of 82
18. Question
What is the value of the gravitational constant?
- a) 6.67 x 10 -10 Nm2kg
- b) 6.67 x 10 -11 Nm2kg-2
- c) 6.67 x 10 17 Nmkg-2
- d) 6.67 x 10 -15 Nm2kg-2
Correct
G is the Gravitational constant that has the value of 6.67 x 10 -11 Nm2kg-2
Incorrect
G is the Gravitational constant that has the value of 6.67 x 10 -11 Nm2kg-2
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Question 19 of 82
19. Question
Which of this planet may experience less gravitational force from the sun?
Correct
As the distance between two masses increases, the strength of the force tends to decrease because of inverse dependence on r2. Physically it implies that the planet Uranus experiences less gravitational force from the Sun than the Earth since Uranus is at larger distance from the Sun compared to the Earth.
Incorrect
As the distance between two masses increases, the strength of the force tends to decrease because of inverse dependence on r2. Physically it implies that the planet Uranus experiences less gravitational force from the Sun than the Earth since Uranus is at larger distance from the Sun compared to the Earth.
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Question 20 of 82
20. Question
Assertion (A): The reaction force is exerted by the Earth on the Sun is directed towards the Earth.
Reasoning(R): The gravitational forces between two particles always constitute an action-reaction pair.
Correct
The gravitational forces between two particles always constitute an action- reaction pair. It implies that the gravitational force exerted by the Sun on the Earth is always towards the Sun. The reaction-force is exerted by the Earth on the Sun. The direction of this reaction force is towards Earth.
Incorrect
The gravitational forces between two particles always constitute an action- reaction pair. It implies that the gravitational force exerted by the Sun on the Earth is always towards the Sun. The reaction-force is exerted by the Earth on the Sun. The direction of this reaction force is towards Earth.
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Question 21 of 82
21. Question
Choose the Incorrect statements.
- i) The Earth’s angular momentum about the Sun is constant throughout the motion.
- ii) The torque experienced by the Earth due to gravitational force of the Sun is a constant scalar.
Correct
The torque experienced by the Earth due to the gravitational force of the Sun is given by L is a constant vector. The angular momentum of the Earth about the Sun is constant throughout the motion. It is true for all the planets. In fact, this constancy of angular momentum leads to the Kepler’s second law.
Incorrect
The torque experienced by the Earth due to the gravitational force of the Sun is given by L is a constant vector. The angular momentum of the Earth about the Sun is constant throughout the motion. It is true for all the planets. In fact, this constancy of angular momentum leads to the Kepler’s second law.
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Question 22 of 82
22. Question
Which of these assumptions is made to calculate the force between the Sun and the Earth?
Correct
- When it is said that Earth orbits around the Sun due to Sun’s gravitational force, we assumed Earth and Sun to be point masses. This assumption is a good approximation because the distance between the two bodies is very much larger than their diameters. For some irregular and extended objects separated by a small distance, we cannot directly use the equation. Instead, we have to invoke separate mathematical treatment which will be brought forth in higher classes.
Incorrect
- When it is said that Earth orbits around the Sun due to Sun’s gravitational force, we assumed Earth and Sun to be point masses. This assumption is a good approximation because the distance between the two bodies is very much larger than their diameters. For some irregular and extended objects separated by a small distance, we cannot directly use the equation. Instead, we have to invoke separate mathematical treatment which will be brought forth in higher classes.
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Question 23 of 82
23. Question
State the Newton’s equation for the centripetal acceleration towards centre for the circular orbit?
- a) a = v3
- b) a = – v2 / r
- c) a = v / r2
- d) a = v r
Correct
Newton considered the orbits of the planets as circular. For circular orbit of radius r, the centripetal acceleration towards the centre is ,
Incorrect
Newton considered the orbits of the planets as circular. For circular orbit of radius r, the centripetal acceleration towards the centre is ,
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Question 24 of 82
24. Question
Assertion (A): The shape of orbits of the planet around the Sun is elliptical.
Reasoning(R): The Planets orbit is very close to being circular as it has small deviation from the circular shape.
Correct
We assumed that the orbit of the planet to be circular which is not true as the orbit of the planet around the Sun is elliptical. But this circular orbit assumption is justifiable because planet’s orbit is very close to being circular and there is only a very small deviation from the circular shape.
Incorrect
We assumed that the orbit of the planet to be circular which is not true as the orbit of the planet around the Sun is elliptical. But this circular orbit assumption is justifiable because planet’s orbit is very close to being circular and there is only a very small deviation from the circular shape.
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Question 25 of 82
25. Question
Who measured the distance between the Earth and the Moon?
Correct
The radius of the Earth was measured by Greek librarian Eratosthenes and distance between the Earth and the Moon was measured by Greek astronomer Hipparchrus 2400 years ago.
Incorrect
The radius of the Earth was measured by Greek librarian Eratosthenes and distance between the Earth and the Moon was measured by Greek astronomer Hipparchrus 2400 years ago.
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Question 26 of 82
26. Question
Assertion (A): The Value of gravitational constant plays an important role in the law of gravitation.
Reasoning(R): The Value of G explains the gravitational force between the Earth and the Sun is so great and between small objects is negligible.
Correct
In the law of gravitation, the value of gravitational constant G plays a very important role. The value of G explains why the gravitational force between the Earth and the Sun is so great while the same force between two small objects (for example between two human beings) is negligible
Incorrect
In the law of gravitation, the value of gravitational constant G plays a very important role. The value of G explains why the gravitational force between the Earth and the Sun is so great while the same force between two small objects (for example between two human beings) is negligible
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Question 27 of 82
27. Question
Who discovered the experimental value of the gravitational constant?
Correct
In the year 1798, Henry Cavendish experimentally determined the value of gravitational constant ‘G’ by using a torsion balance. He calculated the value of ‘G’ to be equal to 6.75 ×10 -11Nm2 kg-2.
Incorrect
In the year 1798, Henry Cavendish experimentally determined the value of gravitational constant ‘G’ by using a torsion balance. He calculated the value of ‘G’ to be equal to 6.75 ×10 -11Nm2 kg-2.
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Question 28 of 82
28. Question
What is the exact accepted value of the gravitational constant?
- a) 66.672 × 10-11 Nmkg-2
- b) 6.67259 ×10-11 Nm2kg-2
- c) 6.67259 x 105
- d) 12.663 ×10-11 Nm2kg-2.
Correct
Using modern techniques a more accurate value of G could be measured. The currently accepted value of G is 6.67259 ×10-11 Nm2kg-2.
Incorrect
Using modern techniques a more accurate value of G could be measured. The currently accepted value of G is 6.67259 ×10-11 Nm2kg-2.
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Question 29 of 82
29. Question
Based on which property the forces are classified?
Correct
Force is basically due to the interaction between two particles. Depending upon the type of interaction we can have two kinds of forces: Contact forces and Non-contact forces.
Incorrect
Force is basically due to the interaction between two particles. Depending upon the type of interaction we can have two kinds of forces: Contact forces and Non-contact forces.
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Question 30 of 82
30. Question
- Assertion (A): Contact forces are applied to object in physical contact with the other object.
- Reasoning(R): The movement of the object is caused by the physical force exerted through the contact.
Correct
Contact forces are the forces applied where one object is in physical contact with the other. The movement of the object is caused by the physical force exerted through the contact between the object and the agent which exerts force.
Incorrect
Contact forces are the forces applied where one object is in physical contact with the other. The movement of the object is caused by the physical force exerted through the contact between the object and the agent which exerts force.
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Question 31 of 82
31. Question
- Assertion (A): The magnitude of E decreases as the distance increases.
- Reasoning(R): The strength of gravitational field decreases as we move away from the mass.
Correct
The strength of the gravitational field decreases as we move away from the mass M as depicted. The magnitude of E decreases as the distance r increases.
Incorrect
The strength of the gravitational field decreases as we move away from the mass M as depicted. The magnitude of E decreases as the distance r increases.
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Question 32 of 82
32. Question
Which of this physical quantity carries energy and momentum in space?
Correct
The “field” concept was introduced as a mathematical tool to calculate gravitational interaction. Later it was found that field is a real physical quantity and it carries energy and momentum in space. The concept of field is inevitable in understanding the behaviour of charges.
Incorrect
The “field” concept was introduced as a mathematical tool to calculate gravitational interaction. Later it was found that field is a real physical quantity and it carries energy and momentum in space. The concept of field is inevitable in understanding the behaviour of charges.
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Question 33 of 82
33. Question
Which of the following has the unit Newton per kilogram?
Correct
The unit of gravitational field is Newton per kilogram (N/kg) or m s-2.
Incorrect
The unit of gravitational field is Newton per kilogram (N/kg) or m s-2.
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Question 34 of 82
34. Question
Choose the correct statements.
- i) The superposition principle of gravitational fields involves the vector sum of the entire gravitational field due to individual masses.
- ii) The total gravitational field at a point is irrespective of all the individual masses.
Correct
Consider ‘n’ particles of masses m1,m 2,… mn distributed in space at position r1, r2,…rn with respect to point P. The total gravitational field at a point P due to all the masses is given by the vector sum of the gravitational field due to the individual masses. This principle is known as superposition of gravitational fields.
Incorrect
Consider ‘n’ particles of masses m1,m 2,… mn distributed in space at position r1, r2,…rn with respect to point P. The total gravitational field at a point P due to all the masses is given by the vector sum of the gravitational field due to the individual masses. This principle is known as superposition of gravitational fields.
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Question 35 of 82
35. Question
- Assertion (A): The gravitational potential energy is always a negative value.
- Reasoning(R): The system does the work when two masses come together from infinity.
Correct
The gravitational potential energy Ur ‑ is always negative because when two masses come together slowly from infinity, work is done by the system.
Incorrect
The gravitational potential energy Ur ‑ is always negative because when two masses come together slowly from infinity, work is done by the system.
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Question 36 of 82
36. Question
Choose the correct statements.
- i) The unit of gravitational potential energy is Joule / s which are a vector quantity.
- ii) The gravitational potential energy depends on the masses and the distance between the masses.
Correct
The unit of gravitational potential energy Ur ‑ is Joule and it is a scalar quantity. The gravitational potential energy depends upon the two masses and the distance between them.
Incorrect
The unit of gravitational potential energy Ur ‑ is Joule and it is a scalar quantity. The gravitational potential energy depends upon the two masses and the distance between them.
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Question 37 of 82
37. Question
- a) – G m1m2 /r
- b) G m1m2 + r
- c) G m1m2 r
- d) G m1m2 / r2
Correct
We can define gravitational potential energy of a system of two masses m1 and m2 separated by a distance r as the amount of work done to take the mass m2 from a distance r to infinity assuming m1 to be fixed in its position and is written as,
Incorrect
We can define gravitational potential energy of a system of two masses m1 and m2 separated by a distance r as the amount of work done to take the mass m2 from a distance r to infinity assuming m1 to be fixed in its position and is written as,
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Question 38 of 82
38. Question
Which of the following value is responsible for the gravitational field?
Correct
The gravitational field E depends only on the source mass which creates the field. It is a vector quantity. We can also define a scalar quantity called “gravitational potential” which depends only on the source mass.
Incorrect
The gravitational field E depends only on the source mass which creates the field. It is a vector quantity. We can also define a scalar quantity called “gravitational potential” which depends only on the source mass.
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Question 39 of 82
39. Question
What is the unit of the gravitational potential?
- a) J s
- b) J kg-1
- c) J / s
- d) J
Correct
The gravitational potential at distance r is equivalent to gravitational potential energy per unit mass at the same distance r. It is a scalar quantity and its unit is J kg-1.
Incorrect
The gravitational potential at distance r is equivalent to gravitational potential energy per unit mass at the same distance r. It is a scalar quantity and its unit is J kg-1.
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Question 40 of 82
40. Question
Choose the Incorrect statements.
- i) The Gravitational field and gravitational force are vector quantities.
- ii) The gravitational potential and gravitational potential energy are scalar quantities.
- iii) The Vector quantities are used for easy analyses of the motion of particles.
Correct
Gravitational field and gravitational force are vector quantities whereas the gravitational potential and gravitational potential energy are scalar quantities. The motion of particles can be easily analysed using scalar quantities than vector quantities.
Incorrect
Gravitational field and gravitational force are vector quantities whereas the gravitational potential and gravitational potential energy are scalar quantities. The motion of particles can be easily analysed using scalar quantities than vector quantities.
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Question 41 of 82
41. Question
- Assertion (A): The gravitation pull produces a constant acceleration in all the bodies near the Earth’s surface.
- Reasoning(R): Newton’s second law states that an object is accelerated only under the action of a force.
Correct
When objects fall on the Earth, the acceleration of the object is towards the Earth. From Newton’s second law, an object is accelerated only under the action of a force. In the case of Earth, this force is the gravitational pull of Earth. This force produces a constant acceleration near the Earth’s surface in all bodies, irrespective of their masses.
Incorrect
When objects fall on the Earth, the acceleration of the object is towards the Earth. From Newton’s second law, an object is accelerated only under the action of a force. In the case of Earth, this force is the gravitational pull of Earth. This force produces a constant acceleration near the Earth’s surface in all bodies, irrespective of their masses.
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Question 42 of 82
42. Question
Which of this value does not depend on the gravitational force exerted by earth near its surface?
Correct
The gravitational force exerted by Earth on the mass m near the surface of the Earth is given by,
ME– mass of the Earth, m-mass of the object, R E– radius of the Earth.
Incorrect
The gravitational force exerted by Earth on the mass m near the surface of the Earth is given by,
ME– mass of the Earth, m-mass of the object, R E– radius of the Earth.
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Question 43 of 82
43. Question
What is the magnitude of the earth’s gravity?
- a) G Me / Re2
- b) G Me3 / Re3
- c) G Me2 / Re
- d) G Me / Re
Correct
The acceleration experienced by the object near the surface of the Earth due to its gravity is called acceleration due to gravity. It is denoted by the symbol g. The magnitude of acceleration due to gravity is g,
Incorrect
The acceleration experienced by the object near the surface of the Earth due to its gravity is called acceleration due to gravity. It is denoted by the symbol g. The magnitude of acceleration due to gravity is g,
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Question 44 of 82
44. Question
Which of this factor does not depend on the mass of an object?
Correct
It is to be noted that the acceleration experienced by any object is independent of its mass. The value of g depends only on the mass and radius of the Earth. In fact Galileo arrived at the same conclusion 400 years ago that all objects fall towards the Earth with the same acceleration through various quantitative experiments.
Incorrect
It is to be noted that the acceleration experienced by any object is independent of its mass. The value of g depends only on the mass and radius of the Earth. In fact Galileo arrived at the same conclusion 400 years ago that all objects fall towards the Earth with the same acceleration through various quantitative experiments.
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Question 45 of 82
45. Question
What is the value of the acceleration due to gravity near Earth equator?
- a) 19.8 m s
- b) 12.8 ms-2
- c) 9.8 m s-2
- d) 6.6 m
Correct
The acceleration due to gravity g is found to be 9.8 m s-2 on the surface of the Earth near the equator.
Incorrect
The acceleration due to gravity g is found to be 9.8 m s-2 on the surface of the Earth near the equator.
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Question 46 of 82
46. Question
Choose the correct statements.
- i) The Earth’s centrifugal force depends on the revolution time.
- ii) The objects on earth’s surface experiences only the centrifugal force of earth’s spinning.
- iii) The centrifugal force on objects on the surface of the Earth depends on the latitude of the object.
Correct
Whenever we analyse the motion of objects in rotating frames we must take into account the centrifugal force. Even though we treat the Earth as an inertial frame, it is not exactly correct because the Earth spins about its own axis. So when an object is on the surface of the Earth, it experiences a centrifugal force that depends on the latitude of the object on Earth. If the Earth were not spinning, the force on the object would have been mg. However, the object experiences an additional centrifugal force due to spinning of the Earth.
Incorrect
Whenever we analyse the motion of objects in rotating frames we must take into account the centrifugal force. Even though we treat the Earth as an inertial frame, it is not exactly correct because the Earth spins about its own axis. So when an object is on the surface of the Earth, it experiences a centrifugal force that depends on the latitude of the object on Earth. If the Earth were not spinning, the force on the object would have been mg. However, the object experiences an additional centrifugal force due to spinning of the Earth.
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Question 47 of 82
47. Question
Which of this value is represented by the symbol λ in the centrifugal force of an object?
Correct
This centrifugal force is given by mω2R‘. R’ = R cos λ where λ is the latitude. The component of centrifugal acceleration experienced by the object in the direction opposite to g.
Incorrect
This centrifugal force is given by mω2R‘. R’ = R cos λ where λ is the latitude. The component of centrifugal acceleration experienced by the object in the direction opposite to g.
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Question 48 of 82
48. Question
At which of the following places the acceleration due to gravity is minimum?
Correct
From the above equation of we can infer that at equator, λ= 0; g’= ‑ g- ω2R. The acceleration due to gravity is minimum. At poles λ= 90; g’ = g, it is maximum. At the equator, g’ is minimum.
Incorrect
From the above equation of we can infer that at equator, λ= 0; g’= ‑ g- ω2R. The acceleration due to gravity is minimum. At poles λ= 90; g’ = g, it is maximum. At the equator, g’ is minimum.
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Question 49 of 82
49. Question
Which of the following is mainly found in earth’s atmosphere?
Correct
Hydrogen and helium are the most abundant elements in the universe but Earth’s atmosphere consists mainly of nitrogen and oxygen.
Incorrect
Hydrogen and helium are the most abundant elements in the universe but Earth’s atmosphere consists mainly of nitrogen and oxygen.
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Question 50 of 82
50. Question
Which of these molecules easily escape from the earth surface?
Correct
Lighter molecules such as hydrogen and helium have enough speed to escape from the Earth unlike the heavier ones such as nitrogen and oxygen. The average speed of hydrogen and helium atoms compared with the escape speed of the Earth is presented in the kinetic theory of gases.
Incorrect
Lighter molecules such as hydrogen and helium have enough speed to escape from the Earth unlike the heavier ones such as nitrogen and oxygen. The average speed of hydrogen and helium atoms compared with the escape speed of the Earth is presented in the kinetic theory of gases.
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Question 51 of 82
51. Question
What is the value of the distance covered by the satellite during one rotation in the orbit?
Correct
Time period of the satellite: The distance covered by the satellite during one rotation in its orbit is equal to 2πRE hand time taken for it is the time period, T. Then Speed v Distance travelled Time taken
Incorrect
Time period of the satellite: The distance covered by the satellite during one rotation in its orbit is equal to 2πRE hand time taken for it is the time period, T. Then Speed v Distance travelled Time taken
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Question 52 of 82
52. Question
What is the value of the total energy of a satellite orbiting the earth?
Correct
The total energy of a satellite orbiting the Earth at a distance h from the surface of Earth is calculated as follows; the total energy of the satellite is the sum of its kinetic energy and the gravitational potential energy.
Incorrect
The total energy of a satellite orbiting the Earth at a distance h from the surface of Earth is calculated as follows; the total energy of the satellite is the sum of its kinetic energy and the gravitational potential energy.
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Question 53 of 82
53. Question
In which of this condition a satellite is free from the Earth’s gravity?
Correct
The total energy of the satellite orbiting the Earth at a height of h is,
Incorrect
The total energy of the satellite orbiting the Earth at a height of h is,
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Question 54 of 82
54. Question
What is the value of h for the geo-stationary satellite?
Correct
Kepler’s third law is used to find the radius of the orbit.
Incorrect
Kepler’s third law is used to find the radius of the orbit.
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Question 55 of 82
55. Question
Which of the following statements are not true regarding the Polar satellites?
Correct
Earth orbits the Earth from north to south direction. This type of satellite that orbits Earth from North Pole to South Pole is called a polar satellite. The time period of a polar satellite is nearly 100 minutes and the satellite completes many revolutions in a day. A Polar satellite covers a small strip of area from pole to pole during one revolution. In the next revolution it covers a different strip of area since the Earth would have moved by a small angle. In this way polar satellites cover the entire surface area of the Earth.
Incorrect
Earth orbits the Earth from north to south direction. This type of satellite that orbits Earth from North Pole to South Pole is called a polar satellite. The time period of a polar satellite is nearly 100 minutes and the satellite completes many revolutions in a day. A Polar satellite covers a small strip of area from pole to pole during one revolution. In the next revolution it covers a different strip of area since the Earth would have moved by a small angle. In this way polar satellites cover the entire surface area of the Earth.
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Question 56 of 82
56. Question
Choose the correct statements.
- i) All the objects anywhere in the solar system experience the gravitational force.
- ii) The Earth gravitational force acts downwards towards the centre of the earth.
- iii) There are number of forces acting on us when we stand on the floor in earth surface.
Correct
Objects on Earth experience the gravitational force of Earth. The gravitational force acting on an object of mass m is mg. This force always acts downwards towards the centre of the Earth. When we stand on the floor, there are two forces acting on us. One is the gravitational force, acting downwards and the other is the normal force exerted by the floor upwards on us to keep us at rest.
Incorrect
Objects on Earth experience the gravitational force of Earth. The gravitational force acting on an object of mass m is mg. This force always acts downwards towards the centre of the Earth. When we stand on the floor, there are two forces acting on us. One is the gravitational force, acting downwards and the other is the normal force exerted by the floor upwards on us to keep us at rest.
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Question 57 of 82
57. Question
Assertion (A): The weight of an object is defined as the upward force with magnitude W is equal to the force.
Reasoning(R): Weight of an object is the upward force applied to hold it at rest or at constant velocity relative to earth.
Correct
The weight of an object W is defined as the downward force whose magnitude W is equal to that of upward force that must be applied to the object to hold it at rest or at constant velocity relative to the earth.
Incorrect
The weight of an object W is defined as the downward force whose magnitude W is equal to that of upward force that must be applied to the object to hold it at rest or at constant velocity relative to the earth.
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Question 58 of 82
58. Question
In which of this direction normal object weight is directed?
Correct
The direction of weight is in the direction of gravitational force. So the magnitude of weight of an object is denoted as, W=N=mg
Incorrect
The direction of weight is in the direction of gravitational force. So the magnitude of weight of an object is denoted as, W=N=mg
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Question 59 of 82
59. Question
Choose the Incorrect statements.
- i) A man standing in an elevator experiences two kinds of forces.
- ii) Gravitational force on the man in an elevator is acting downwards to the ground.
- iii) The Normal force exerted by the floor also acts downwards to the man in an elevator.
Correct
Incorrect
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Question 60 of 82
60. Question
- Assertion (A): The Astronauts in the satellites do not experience any gravitational force due to the distance from the earth.
- Reasoning(R): The Satellites orbit very close to Earth experience only gravitational force.
Correct
There is a wrong notion that the astronauts in satellites experience no gravitational force because they are far away from the Earth. Actually the Earth satellites that orbit very close to Earth experience only gravitational force. The astronauts inside the satellite also experience the same gravitational force. Because of this, they cannot exert any force on the floor of the satellite. Thus, the floor of the satellite also cannot exert any normal force on the astronaut. Therefore, the astronauts inside a satellite are in the state of weightlessness. Not only the astronauts, but all the objects in the satellite will be in the state of weightlessness which is similar to that of a free fall.
Incorrect
There is a wrong notion that the astronauts in satellites experience no gravitational force because they are far away from the Earth. Actually the Earth satellites that orbit very close to Earth experience only gravitational force. The astronauts inside the satellite also experience the same gravitational force. Because of this, they cannot exert any force on the floor of the satellite. Thus, the floor of the satellite also cannot exert any normal force on the astronaut. Therefore, the astronauts inside a satellite are in the state of weightlessness. Not only the astronauts, but all the objects in the satellite will be in the state of weightlessness which is similar to that of a free fall.
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Question 61 of 82
61. Question
Towards which of this direction the planets move in the retrograde motion?
Correct
When the motion of the planets are observed in the night sky by naked eyes over a period of a few months, it can be seen that the planets move eastwards and reverse their motion for a while and return to eastward motion again. This is called “retrograde motion” of planets.
Incorrect
When the motion of the planets are observed in the night sky by naked eyes over a period of a few months, it can be seen that the planets move eastwards and reverse their motion for a while and return to eastward motion again. This is called “retrograde motion” of planets.
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Question 62 of 82
62. Question
From which month the Mars changes its direction from retrograde motion?
Correct
Careful observation for a period of a year clearly shows that Mars initially moves eastwards (February to June), then reverses its path and moves backwards (July, August, September). It changes its direction of motion once again and continues its forward motion (October onwards).
Incorrect
Careful observation for a period of a year clearly shows that Mars initially moves eastwards (February to June), then reverses its path and moves backwards (July, August, September). It changes its direction of motion once again and continues its forward motion (October onwards).
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Question 63 of 82
63. Question
Which of the following concept was introduced by Ptolemy to explain the retrograde motion of the planets?
Correct
To explain this retrograde motion, Ptolemy introduced the concept of “epicycle” in his geocentric model. According to this theory, while the planet orbited the Earth, it also underwent another circular motion termed as “epicycle”.
Incorrect
To explain this retrograde motion, Ptolemy introduced the concept of “epicycle” in his geocentric model. According to this theory, while the planet orbited the Earth, it also underwent another circular motion termed as “epicycle”.
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Question 64 of 82
64. Question
Choose the incorrect statements.
- i) The retrograde motion of the planets is a combination of epicycle and circular motion around the Earth.
- ii) The Earth centric idea was introduced by Aristotle.
- iii) Ptolemy’s model was very simple as every planet undergoes the retrograde motion.
Correct
A combination of epicycle and circular motion around the Earth gave rise to retrograde motion of the planets with respect to Earth. Essentially Ptolemy retained the Earth centric idea of Aristotle and added the epicycle motion to it. Ptolemy’s model became more and more complex as every planet was found to undergo retrograde motion.
Incorrect
A combination of epicycle and circular motion around the Earth gave rise to retrograde motion of the planets with respect to Earth. Essentially Ptolemy retained the Earth centric idea of Aristotle and added the epicycle motion to it. Ptolemy’s model became more and more complex as every planet was found to undergo retrograde motion.
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Question 65 of 82
65. Question
Which of these is the centre of the solar system according to the heliocentric model of Copernicus?
Correct
In the 15th century, the Polish astronomer Copernicus proposed the heliocentric model to explain this problem in a simpler manner. According to this model, the Sun is at the centre of the solar system and all planets orbited the Sun. The retrograde motion of planets with respect to Earth is because of the relative motion of the planet with respect to Earth.
Incorrect
In the 15th century, the Polish astronomer Copernicus proposed the heliocentric model to explain this problem in a simpler manner. According to this model, the Sun is at the centre of the solar system and all planets orbited the Sun. The retrograde motion of planets with respect to Earth is because of the relative motion of the planet with respect to Earth.
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Question 66 of 82
66. Question
Choose the correct statements.
- i) Copernicus explained the retrograde motion of the Mars and Earth only.
- ii) The Mars orbits around the Sun faster than the Earth.
- iii) Mars appears to move backwards from July to October because of the relative motion of the Earth and Mars.
Correct
Explanation
The Earth orbits around the Sun faster than Mars. Because of the relative motion between Mars and Earth, Mars appears to move backwards from July to October. In the same way the retrograde motion of all other planets was explained successfully by the Copernicus model.
Incorrect
Explanation
The Earth orbits around the Sun faster than Mars. Because of the relative motion between Mars and Earth, Mars appears to move backwards from July to October. In the same way the retrograde motion of all other planets was explained successfully by the Copernicus model.
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Question 67 of 82
67. Question
What is the advantage of the heliocentric model?
Correct
It was because of its simplicity, the heliocentric model slowly replaced the geocentric model. Historically, if any natural phenomenon has one or more explanations, the simplest one is usually accepted.
Incorrect
It was because of its simplicity, the heliocentric model slowly replaced the geocentric model. Historically, if any natural phenomenon has one or more explanations, the simplest one is usually accepted.
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Question 68 of 82
68. Question
Which of the following statement is not true?
Correct
When Kepler derived his three laws, he strongly relied on Tycho Brahe’s astronomical observation. In his third law, he formulated the relation between the distances of a planet from the Sun to the time period of revolution of the planet. Astronomers cleverly used geometry and trigonometry to calculate the distance of a planet from the Sun in terms of the distance between Earth and Sun.
Incorrect
When Kepler derived his three laws, he strongly relied on Tycho Brahe’s astronomical observation. In his third law, he formulated the relation between the distances of a planet from the Sun to the time period of revolution of the planet. Astronomers cleverly used geometry and trigonometry to calculate the distance of a planet from the Sun in terms of the distance between Earth and Sun.
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Question 69 of 82
69. Question
What is the distance between the Earth and the Sun?
Correct
When Venus is at maximum elongation (i.e., 46 degree) with respect to Earth, Venus makes 90 degree to Sun. This allows us to find the distance between Venus and Sun. The distance between Earth and Sun is taken as one Astronomical unit (1 AU).
Incorrect
When Venus is at maximum elongation (i.e., 46 degree) with respect to Earth, Venus makes 90 degree to Sun. This allows us to find the distance between Venus and Sun. The distance between Earth and Sun is taken as one Astronomical unit (1 AU).
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Question 70 of 82
70. Question
Which of the following planets have the highest value of the semi major axis of the orbit from the Sun?
Correct
Incorrect
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Question 71 of 82
71. Question
Identify the Incorrect Match.
- PLANETS TIME PERIOD
- Saturn i) 4332.62
- Mercury ii) 87.77
- Venus iii) 224.70
- Mars iv) 686.98
Correct
The distances of planets from the Sun are given in the table below.
Incorrect
The distances of planets from the Sun are given in the table below.
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Question 72 of 82
72. Question
Which of these values denotes the difference in sun ray shadow due to the curvature of the Earth?
Correct
During noon time of summer solstice the Sun’s rays cast no shadow in the city Syne which was located 500 miles away from Alexandria. At the same day and same time he found that in Alexandria the Sun’s rays made 7.2 degree with local vertical. This difference of 7.2 degree was due to the curvature of the Earth. The angle 7.2 degree is equivalent to 1/8radian. So θ= 1/8 rad;
Incorrect
During noon time of summer solstice the Sun’s rays cast no shadow in the city Syne which was located 500 miles away from Alexandria. At the same day and same time he found that in Alexandria the Sun’s rays made 7.2 degree with local vertical. This difference of 7.2 degree was due to the curvature of the Earth. The angle 7.2 degree is equivalent to 1/8radian. So θ= 1/8 rad;
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Question 73 of 82
73. Question
In which colour the moon will appear inside the umbra shadow?
Correct
When the Moon is inside the umbra shadow, it appears red in colour. As soon as the Moon exits from the umbra shadow, it appears in crescent shape.
Incorrect
When the Moon is inside the umbra shadow, it appears red in colour. As soon as the Moon exits from the umbra shadow, it appears in crescent shape.
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Question 74 of 82
74. Question
Assertion (A): During the lunar eclipse the orbits of the Moon and Earth lie on the same plane on full moon day.
Reasoning(R): The Solar eclipse is observed during the new moon day.
Correct
If the orbits of the Moon and Earth lie on the same plane, during full Moon of every month, we can observe lunar eclipse. If this is so during new Moon we can observe solar eclipse.
Incorrect
If the orbits of the Moon and Earth lie on the same plane, during full Moon of every month, we can observe lunar eclipse. If this is so during new Moon we can observe solar eclipse.
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Question 75 of 82
75. Question
Why Solar and Lunar eclipse occur only during certain periods of the year?
Correct
Moon’s orbit is tilted 5° with respect to Earth’s orbit. Due to this 5° tilt, only during certain periods of the year, the Sun, Earth and Moon align in straight line leading to either lunar eclipse or solar eclipse depending on the alignment.
Incorrect
Moon’s orbit is tilted 5° with respect to Earth’s orbit. Due to this 5° tilt, only during certain periods of the year, the Sun, Earth and Moon align in straight line leading to either lunar eclipse or solar eclipse depending on the alignment.
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Question 76 of 82
76. Question
- Assertion (A): The Northern and the Southern part of the Earth experiences seasonal changes depending on the distance from the Sun.
- Reasoning(R): The seasons in the Earth arise due to the rotation of the Earth around the Sun with 23.5° tilt.
Correct
The seasons in the Earth arise due to the rotation of Earth around the Sun with 23.5° tilt Due to this 23.5° tilt, when the northern part of Earth is farther to the Sun, the southern part is nearer to the Sun. So when it is summer in the northern hemisphere, the southern hemisphere experience winter.
Incorrect
The seasons in the Earth arise due to the rotation of Earth around the Sun with 23.5° tilt Due to this 23.5° tilt, when the northern part of Earth is farther to the Sun, the southern part is nearer to the Sun. So when it is summer in the northern hemisphere, the southern hemisphere experience winter.
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Question 77 of 82
77. Question
Which of these can be explained by the spinning motion of Earth?
Correct
The Earth’s spinning motion can be proved by observing star’s position over a night. Due to Earth’s spinning motion, the stars in sky appear to move in circular motion about the pole star.
Incorrect
The Earth’s spinning motion can be proved by observing star’s position over a night. Due to Earth’s spinning motion, the stars in sky appear to move in circular motion about the pole star.
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Question 78 of 82
78. Question
Name the pole star of the Earth.
Correct
Pole star is a star located exactly above the Earth’s axis of rotation hence it appears to be stationary. The Star Polaris is our pole star.
Incorrect
Pole star is a star located exactly above the Earth’s axis of rotation hence it appears to be stationary. The Star Polaris is our pole star.
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Question 79 of 82
79. Question
Choose the Incorrect statements.
- i) The Electromagnetic spectrum was discovered at the end of the 19th
- ii) Newton’s law of gravitation was able to explain the entire phenomenon related to gravity.
- iii) Albert Einstein General relativity theory was the most successful theory in the 20th century.
Correct
After the discovery of the electromagnetic spectrum at the end of the 19th century, our understanding of the universe increased enormously. Because of this development in the late 19th century it was found that Newton’s law of gravitation could not explain certain phenomena and showed some discrepancies. Albert Einstein formulated his ‘General theory of relativity’ which was one of the most successful theories of 20th century in the field of gravitation.
Incorrect
After the discovery of the electromagnetic spectrum at the end of the 19th century, our understanding of the universe increased enormously. Because of this development in the late 19th century it was found that Newton’s law of gravitation could not explain certain phenomena and showed some discrepancies. Albert Einstein formulated his ‘General theory of relativity’ which was one of the most successful theories of 20th century in the field of gravitation.
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Question 80 of 82
80. Question
For which of the following theories Subramanian Chandrasekhar was awarded Nobel Prize in the year 1983?
Correct
Subramanian Chandrasekhar formulated the theory of black holes and explained the life of stars. These studies brought him the Nobel Prize in the year 1983. Another very notable Indian astrophysicist Meghnad Saha discovered the ionization formula which was useful in classifying stars. This formula is now known as “Saha ionization formula”.
Incorrect
Subramanian Chandrasekhar formulated the theory of black holes and explained the life of stars. These studies brought him the Nobel Prize in the year 1983. Another very notable Indian astrophysicist Meghnad Saha discovered the ionization formula which was useful in classifying stars. This formula is now known as “Saha ionization formula”.
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Question 81 of 82
81. Question
Choose the correct statements.
- i) Amal Kumar Raychaudhuri solved an equation, Raychaudhuri equation in the field of gravitation.
- ii) The Astrophysicist Jayant V Narlikar wrote books on astronomy and astrophysics.
Correct
In the field of gravitation Amal Kumar Raychaudhuri solved an equation now known as “Raychaudhuri equation” which was a very important contribution. Another notable Indian Astrophysicist Jayant V Narlikar made pioneering contribution in the field of astrophysics and has written interesting books on astronomy and astrophysics.
Incorrect
In the field of gravitation Amal Kumar Raychaudhuri solved an equation now known as “Raychaudhuri equation” which was a very important contribution. Another notable Indian Astrophysicist Jayant V Narlikar made pioneering contribution in the field of astrophysics and has written interesting books on astronomy and astrophysics.
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Question 82 of 82
82. Question
Who founded the Inter University Centre for Astronomy and Astrophysics, India?
Correct
IUCAA (Inter University Centre for Astronomy and Astrophysics) is one of the important Indian research institutes where active research in astrophysics and gravitation are conducted. The institute was founded by Prof. J.V. Narlikar. Students are encouraged to read more about the recent developments in these fields.
Incorrect
IUCAA (Inter University Centre for Astronomy and Astrophysics) is one of the important Indian research institutes where active research in astrophysics and gravitation are conducted. The institute was founded by Prof. J.V. Narlikar. Students are encouraged to read more about the recent developments in these fields.
Leaderboard: Gravitation 11th Science Lessons
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